One of the main challenges facing the Office of Naval Research is the development of an inexpensive, environmentally friendly, robust “coating” that can minimize adhesion of native marine species onto the coated surface. Current antifouling approaches work to some degree; however, they all exhibit several drawbacks including: high cost, coating material leaching, ocean pollution, and/or poor surface-to-film stability.
Oxidized sea water, produced by electrolysis or ozonolysis has been used to prevent biofouling on flat surfaces, especially in connection with cooling water intakes of coastal power plants (Allonier et al., J. Rech. Oceanogr. 23:21 et al. (1998); Baboian et al., Mater. Perform. 19:42 et al. (1980); Johnson et al., Energy Res. Abstr. 8, Abstract 10409 (1983)). As a consequence of this application, a significant body of information has been generated with respect to the chemistry associated with the antifouling agents and to their environmental impact. Oxidized seawater involves the equilibria between elemental halogens and water and the corresponding hypochlorous or hypobromous acid. Near the ocean surface, hypochlorous acid/hypochlorite will oxidize bromide to give hypobromous acid/hypobromite with the kinetics of oxidation dependent upon pH, temperature, and halide ion concentrations (Sugum et al., Chemospere 10:41 et al. (1981); Fisher et al., Water Res. 33:760 et al. (1998, Volume Date 1999)). Thus, the oxidation of either chloride or bromide contained in seawater will produce hypobromous acid as the primary biocide.
The hypohalous acids are produced naturally at low concentrations in seawater. Ocean water is approximately 0.5 M in chloride, 1 mM in bromide, and 1 μM in iodide (Butler et al., Chem. Rev. 93:1937 et al. (1993)). Near the surface (0 to 25 meters), ocean water contains 1-2×10−7 M (0.1-0.2 μM) hydrogen peroxide (Zika et al., Geochim. Cosmochim. Acta 49:1173 et al. (1985)). The photo-oxidation of organic matter in seawater is thought to be the major source of hydrogen peroxide in the ocean via the formation of superoxide, which gives molecular oxygen and hydrogen peroxide in the presence of a proton source (Zika, EOS 61:1010 et al. (1980); Cooper et al., Science 220:711 et al. (1983); Draper et al., Agric. Food. Chem. 31:734 et al. (1983); Draper et al., Arch. Environ. Contam. Toxicol 2:121 et al. (1983)). Chloride, bromide, and iodide are slowly oxidized by hydrogen peroxide in the absence of a catalyst to give the corresponding hypohalous acid (Leulier, Bull. Soc. Chim. Fr. 35:1325 et al. (1924); Mohammed et al., J. Am. Chem. Soc. 56:1680 et al. (1934)). Nature has taken full advantage of these resources through the evolution of the haloperoxidase enzymes, which produce the halometabolites found in many marine organisms via the enzymatic production of positive halogen species (Butler et al., Chem. Rev. 93:1937 et al. (1993); Butler et al., Coord. Chem. Rev. 109:61 et al. (1991); Wever et al., Chasten, ed., in Vanadium in Biological Systems, Kluwer Academic Publishers Dordrecht, The Netherlands, pp. 81-97 (1990); Butler, Reedijk, ed., in Bioinorganic Catalysis, Marcel Dekker: New York, N.Y., pp. 425-445 (1992)).
Once produced, the hypohalous acids/hypohalites enter a many faceted degradation scheme. As shown in equations 1-3, bromide acts as a catalyst for the degradation of hydrogen peroxide through the intermediacy of hypobromous acid (Butler et al., Chem. Rev. 93:1937 et al. (1993); Leulier, Bull. Soc. Chim. Fr. 35:1325 et al. (1924); Mohammed et al., J. Am. Chem. Soc. 56:1680 et al. (1934); Butler et al., Coord. Chem. Rev. 109:61 et al. (1991); Wever et al., Chasten, ed., in Vanadium in Biological Systems, Kluwer Academic Publishers: Dordrecht, The Netherlands, pp. 81-97 (1990); Butler, Reedijk, ed., in Bioinorganic Catalysis, Marcel Dekker: New York, N.Y., pp. 425-445 (1992)):H2O2+NaBr→HOBr+NaOH  (1)HOBr+H2O2→H2O+HBr+O2  (2)2H2O2→2H2O+O2  (3)Other degradation reactions for hypohalous acids involve reduction to halide salts and water in the presence of natural reducing agents (Jaworske et al., Environ. Sci. Technol 19:1188 et al. (1985)), loss to the atmosphere (as Cl2 or Br2) (Helz et al., Gov. Rep. Announce. Index 81:2634 et al. (1981)), reactions with ambient ammonia to produce halamines (with oxidation of bromide by hypochlorite being more rapid than production of CINH2 from NH3) (Sugum et al., Water Chlorination: Environ. Impact Health Eff 3:427 et al. (1980)), and decarboxylation of amino acids found in organic matter near the surface (Helz et al., Water Chlorination: Environ. Impact Health Eff 3:387 et al. (1980); Dotson et al., Water Chlorination: Environ. Impact Health Eff 5:713 et al. (1985)). The production of polyhaloalkanes is a minor degradation process, accounting for less than 4% of the degradation products from hypohalous acids (Helz et al., Water Chlorination: Environ. Impact Health Eff 3:387 et al. (1980); Dotson et al., Water Chlorination: Environ. Impact Health Eff 5:713 et al. (1985)). Furthermore, the degradation of hypobromous acid/hypobromite as well as bromamine derivatives was found to be 2 to 5 times faster than degradation of hypochlorous acid/hypochlorite in the marine environment (Allonier et al., J. Rech. Oceanogr. 23:21 et al. (1998); Fisher et al., Water Res. 33:760 et al. (1998, Volume Date 1999)).
One environmental concern with the use of hypohalous acids as an antifoulant in coastal power plant cooling towers is the effect of higher concentrations of hypohalous acids on local marine organisms (Fisher et al., Water Res. 33:760 et al. (1998, Volume Date 1999); Mimura et al., Suisan Zoshaku 46, 579 et al. (1998)). Electrolysis procedures generate hypohalous acids continuously as long as the electrolysis current flows. At concentrations of hypohalous acid greater than 40 μM, delayed hatching in several species of fish eggs has been noted (Mimura et al., Suisan Zoshaku 46, 579 et al. (1998)). However, concentrations as low as 0.1 μM have been effective at minimizing the adhesion of marine organisms in cooling water intakes.
Chemists have sought to mimic the halogenation reactions employed by marine organisms in the laboratory. Recent efforts in this area have involved chloroperoxidase (Dexter et al., J. Am. Chem. Soc. 117:6412 et al. (1995); Allain et al., J. Am. Chem. Soc. 115:4415 et al. (1993)) and bromoperoxiadse (Butler et al., Chem. Rev. 93:1937 et al. (1993); Leulier, Bull. Soc. Chim. Fr. 35:1325 et al. (1924); Mohammed et al., J. Am. Chem. Soc. 56:1680 et al. (1934)) enzymes and model systems to mimic their activity (Collman et al., J. Am. Chem. Soc. 117:692 et al. (1995); Palucki et al., J. Am. Chem. Soc. 116:9333 et al. (1994); Jacobsen et al., J. Am. Chem. Soc. 113:7063 et al. (1991); Lee et al., Tetrahedron Lett 32:6533 et al. (1991); Andersson et al., Tetrahedron Lett 36:2675 et al. (1995); Clague et al., J. Am. Chem. Soc. 117:3563 et al. (1995); Meister et al., Inorg. Chem. 33:3269 et al. (1994); Colpas et al., J. Am. Chem. Soc. 116:3627 et al. (1994); Reynolds et al., Inorg. Chem. 33:4977 et al. (1994); Espenson et al., J. Am. Chem. Soc. 116:2869 et al. (1994); Ma et al., Inorg. Chem. 31:1925 et al. (1992); de la Rosa et al., J. Am. Chem. Soc. 114:760 et al. (1992)). These systems use a transition metal (heme-bound iron for chloroperoxidase, non-heme vanadium for bromoperoxidase) (Butler et al., Chem. Rev. 93:1937 et al. (1993)) to activate hydrogen peroxide for the oxidation of halide to halogen or halohydrin, which can then react with an appropriate substrate. Model studies have shown that chloride (Soedjak et al., Inorg. Chem. 29:5015 et al. (1990)), bromide (Butler et al., Chem. Rev. 93:1937 et al. (1993); Leulier, Bull. Soc. Chim. Fr. 35:1325 et al. (1924); Mohammed et al., J. Am. Chem. Soc. 56:1680 et al. (1934); Andersson et al., Tetrahedron Lett 36:2675 et al. (1995); Clague et al., J. Am. Chem. Soc. 117:3563 et al. (1995); Meister et al., Inorg. Chem. 33:3269 et al. (1994); Colpas et al., J. Am. Chem. Soc. 116:3627 et al. (1994); Reynolds et al., Inorg. Chem. 33:4977 et al. (1994); Espenson et al., J. Am. Chem. Soc. 116:2869 et al. (1994); Ma et al., Inorg. Chem. 31:1925 et al. (1992); de la Rosa et al., J. Am. Chem. Soc. 114:760 et al. (1992)), and iodide (Secco, Inorg. Chem. 19:2722 et al. (1980); Arias et al., Can. J. Chem. 68:1499 et al. (1990)) can be oxidized by such catalysts and that the metal undergoes sequential one-electron steps. These biomimetic reactions are important to chemistry in general because they perform many desired chemical transformations such as epoxidations and halogenations in an environmentally acceptable way by avoiding unneeded byproducts and by using water as the solvent. However, the one-electron steps at the transition metal can lead to reactions derived from halogen radicals that may destroy the active catalyst.
The present invention is directed to overcoming these and other deficiencies in the art.